The Early Life of Robert Southey, 1774–1803 (New York: Columbia University Press, 1917).
Tracts on Liberty in the Puritan Revolution, three volumes (New York: Columbia University Press, 1934).
The Rise of Puritanism, or, the Way to the New Jerusalem as Set Forth in Pulpit and Press from Thomas Cartwright to John Lilburne and John Milton, 1570–1643 (New York: Columbia University Press, 1938).
The Leveller Tracts, 1647–1653, co-edited with Godfrey Davies (New York: Columbia University Press, 1944).
Liberty and Reformation in the Puritan Revolution (New York: Columbia University Press, 1955).
Foxe's Book of Martyrs and the Elect Nation (London: Jonathan Cape, 1963).
Elizabeth I and the Puritans (Ithaca, New York: Cornell University Press, 1964).